Greubel Forsey GMT White Gold

Launched in 2011, the GMT White gold model by Greubel Forsey features a number of complications and functions such as: 2nd time zone GMT display, Tourbillon 24 Secondes, rotating globe with universal time display, 24 time zone world-time display, summer time indicator, world-time disc with summer time zones, day-and-night indicator, power-reserve indicator, hour and minute display, small second indicator, GMT pusher and lastly the equatorial sapphire crystal lateral window.
This grand complication model is equipped with a mechanical hand-wound movement, Calibre GF05 that is made of 436 parts. Greubel Forsey GMT model comes in 43.50 mm white gold case featuring asymmetrical convex sapphire crystal and three-dimensional, variable geometry-shaped lugs.

The specially developed movement of the GMT features the 25° inclined Tourbillon 24 Secondes cage, one of Greubel Forsey’s major patented inventions. In addition to its superb chronometric virtues and reliability, its compact size allows space for the other complications.

Spatially, the combination of elements on the dial-side is perfectly balanced, with a striking sense of depth offered by the globe and by the Tourbillon 24 Secondes at 5 o’clock which together form a triple asymmetry giving rise to a controlled tension that plays subtly with the circularity of the case, while never totally rupturing it.

Turning over the GMT reveals the beautifully crafted ‘worldtime’ disc bearing the names of 24 cities each representing one of the different global time zones. Aligning the relevant city with the local hour on the outer chapter ring – or inner ring for cities with summer time – sets the dial-side globe in the correct position.

Completing the display-back is a gleaming sun, providing a visual reference for midday on the worldtime disc and radiantly lighting up the movement of this stunning timepiece.

The GMT is reinforced by the hallmarks of Greubel Forsey’s renowned superlative fine finishing and attention to detail. The full range of traditional hand-finishing techniques have been employed including graining, bevelling, polishing, lapping, frosting and flat black polishing – a beautiful demonstration of savoir-faire in the pursuit of excellence.

On the technical side, the movement consists of 436 components, 87 of which are used in the tourbillon cage, which weighs in at just 0.36 grams. Two coaxial mainspring barrels connected in series provide a power reserve of 72 hours and the movement is equipped with a variable inertia balance beating at 21,600vph/3Hz and a Phillips terminal curve balance spring.

Plates and bridges are hand-finished, frosted, spotted, bevelled, straight-grained, matt lapped and flat black polished. The dial is in 18k gold and the whole movement is housed in a white gold case of 43.50mm in diameter with a height of 16.14mm. The case is completed by domed sapphire crystals for the dial-side, display-back and lateral window, all treated with anti-reflective coating. The timepiece is complemented by a hand-sewn black alligator leather strap with a Greubel Forsey folding clasp in white gold.

Technical details

Functions
2nd time zone GMT display
Tourbillon 24 Secondes
Rotating globe with universal time display
24 time zone world time display
Summer time indicator
World time disc with summer time zones
Day-and-night indicator
Power-reserve indicator
Hour and minute display
Small second indicator
GMT pusher
Equatorial sapphire crystal lateral window

Movement
Mechanical hand-wound movement, Calibre GF05
2 patents pending, Movement with patented tourbillon
Diameter: 36.40 mm, Thickness: 12.46 mm

Number of parts
Complete movement: 436 parts, Tourbillon cage: 87 parts
– Weight of the cage: 0.36 g
– Number of jewels: 50, Olived-domed jewels in gold chatons

Power reserve: 72 hours
Barrels: Two coaxial series-coupled fast-rotating barrels (1 turn in 3.2 hours), one of which is equipped with a slipping spring to avoid excess tension
Balance wheel: Free sprung variable-inertia balance with gold meantime screws (10 mm diameter)
Frequency: 21’600 vibrations/hour
Balance spring: Phillips terminal curve, Geneva-style stud
Main Plates: Nickel silver, frosted and spotted with polished beveling and countersinks, straight-grained flanks, nickel palladium-finish

Bridges
• Nickel silver, frosted and spotted, nickel-palladium finish, hand-bevelled, straight-grained flanks, polished countersinks
• Gold nameplates bearing the individual number of the timepiece
• Flat black polished steel tourbillon bridge, hand-bevelled

Gearing
• Involute circle profile
• Conical gearing with corrected profiles

Tourbillon cage
• Inclined at a 25° angle, 24-second rotation
• Cage pillars in Avional
• Titanium cage bridges
• Gold counterweight

Displays
Hour and minute
Small second
72-hour power reserve on a sector
2nd time zone GMT indicator
24 time zone worldtime display
Rotating globe with universal time display
Summer time indicator
Day-and-night indicator

Case
White gold with asymmetrical convex sapphire crystal
Transparent back with asymmetrical convex sapphire crystal
Three-dimensional, variable geometry-shaped lugs
Polished bezel and centre band with hand-finished straight graining
Lateral window with shaped sapphire crystal
White gold pusher with raised polished engraving “GMT“ on a hand-punched background
Raised polished engraving “Greubel Forsey” on a hand-punched background
Hand-engraved individual number
Gold security screws
Case dimensions: Diameter: 43.50 mm, Thickness: 16.14 mm
Water resistance of the case: 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown: In white gold with engraved and black lacquered GF logo

Dial
Principal hour-minute dial in gold, frosted, anthracite finish (NAC).
Hour indicator: white gold, circular graining.
Gold power reserve sector, matt lapped
Gold small second indicator, matt lapped
Gold GMT indicator, matt lapped
Applied gold Greubel Forsey logo

Hands
Hour and minute in polished gold, with Super- Luminova
Small second and power-reserve in blued steel
2nd time zone GMT indicator, red triangle

Strap and clasp
Hand-sewn blue or black alligator
White gold folding clasp, hand-engraved with the Greubel Forsey logo

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